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March 2003

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Subject:
From:
Steve Thomas <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Tue, 11 Mar 2003 09:42:03 -0800
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text/plain
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text/plain (73 lines)
Tom,

Re: both your scenarios, those seem sensible to me, but of course I'm somewhat 
biased because we take it even a step further.  

We use ws paste on a number of boards in SMT (they are washed prior to any pth 
assembly), but use nc flux in our wave solder machines. We also do any 
repairs or hand soldering steps downstream from wave with nc cored wire.

I guess the deciding factor is that because the residues from the ws SMT process are 
removed, there is no combining, mixing, etc., of dissimilar flux types. 


-----Original Message-----
From: Tom Parkinson - Quality System Manager - WinTronics, Inc.
[mailto:[log in to unmask]]
Sent: Tuesday, March 11, 2003 8:39 AM
To: [log in to unmask]
Subject: Re: [TN] Mixing fluxes - more


I've read the recent questions and information concerning mixing of
fluxes.  I agree - do not mix flux types when soldering.  However,
here's one for you that can be looked at from a couple of angles....

1. I build a board - wave solder using washable flux.  Flux is
activated, does it's thing, and board is soldered.
2. Water Wash and Dry the board. All washable flux residue is gone.
3. Add a couple of more components that CANNOT be washed (water will
enter the component and ruin it), using NO-CLEAN.
4. Board is done.

Technically, I have used 2 types of fluxes on one assembly....

Another scenario:
1. Board (described above) is finished.  But, fails test - I find a bad
component...
2. I have to use NO CLEAN to replace the component because I cannot
water wash the board (remember the other components that cannot be
subjected to water wash..)
3. Board is done. Passes test - finished.

Again - Technically, I have mixed fluxes on the same assembly.

In the above description, I do not see a problem - or am I missing
something?


Thanks,
Tom

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